Drop old annotation parser implementation

[coord-e]

Replace src/annot.rs with the annotation parsing mechanism introduced in #57

• Replace all annotations in test cases with the new annotation parser Replace thrust:: with thrust_macros:: for requires/ensures in UI tests #85
• Implement thrust::param and thrust::ret using the new annotation parser Add param/ret/sig refinement-type annotations via thrust_macros #98
• Update documentation docs: update annotation documentation for the new macro-based syntax #111